How to change the color of UIPickerView Selector

Maybe it's not fully fits for answer to this question, in iOS 7 and later you can customize color by this way:

In the delegate methods

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component

add following

[[pickerView.subviews objectAtIndex:1] setBackgroundColor:NEEDED_COLOR];
[[pickerView.subviews objectAtIndex:2] setBackgroundColor:NEEDED_COLOR];

UPDATE

Previous code works, but so-so. Here simple subclasses for UIPickerView

Swift:

class RDPickerView: UIPickerView
{
    @IBInspectable var selectorColor: UIColor? = nil

    override func didAddSubview(subview: UIView) {
        super.didAddSubview(subview)
        if let color = selectorColor
        {
            if subview.bounds.height <= 1.0
            {
                subview.backgroundColor = color
            }
        }

    }
}

Objective-C:

@interface RDPickerView : UIPickerView

@property (strong, nonatomic) IBInspectable UIColor *selectorColor;

@end

@implementation RDPickerView

- (void)didAddSubview:(UIView *)subview
{
    [subview didAddSubview:subview];
    if (self.selectorColor)
    {
        if (subview.bounds.size.height <= 1.0)
        {
            subview.backgroundColor = self.selectorColor;
        }
    }
}

@end

and you can set selector color directly in storyboard

Thanks to Ross Barbish - "With iOS 9.2 and XCode 7.2 released 12/8/2015, the height of this selection view is 0.666666666666667".

UPDATE:

It's fix for issue with iOS 10, not good but works. :/

class RDPickerView: UIPickerView
{
    @IBInspectable var selectorColor: UIColor? = nil

    override func didAddSubview(_ subview: UIView) {
        super.didAddSubview(subview)

        guard let color = selectorColor else {
            return
        }

        if subview.bounds.height <= 1.0
        {
            subview.backgroundColor = color
        }
    }

    override func didMoveToWindow() {
        super.didMoveToWindow()

        guard let color = selectorColor else {
            return
        }

        for subview in subviews {
            if subview.bounds.height <= 1.0
            {
                subview.backgroundColor = color
            }
        }
    }
}

Thanks Dmitry Klochkov, I'll try to find some better solution.

Here's an improvement to vsilux's answer, in form of a simple category to UIPickerView, without the need to subclass UIPickerView.

(Up-to-date answer as of November 2, 2018)

Swift 4, Xcode 10:

@IBInspectable var selectorColor: UIColor? {
    get {
        return objc_getAssociatedObject(self, &selectorColorAssociationKey) as? UIColor
    }
    set(newValue) {
        objc_setAssociatedObject(self, &selectorColorAssociationKey, newValue,
                                 objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN)
    }
}

open override func didAddSubview(_ subview: UIView) {

    super.didAddSubview(subview)
    if let color = selectorColor {
        if subview.bounds.height < 1.0 {
            subview.backgroundColor = color
        }
    }
}

I suppose you're dealing with the iPhone SDK? There may be some other frameworks which uses this name, so maybe you can add your tags to include uikit, cocoa-touch or something.

Anyway, you can set showsSelectionIndicator of the UIPickerView instance to NO, so it hides the selector. Then you can create a new view with the adjusted selection style, and add it to the superview above the UIPickerView.

// Some sample code, but you can do this in IB if you want to
_pickerView = [[UIPickerView alloc] init];
_pickerView.showsSelectionIndicator = NO;
[_pickerView sizeToFit];
[self.view addSubview:_pickerView];

UIImage *selectorImage = [UIImage imageNamed:@"selectorImage.png"]; // You have to make it strechable, probably
UIView *customSelector = [[UIImageView alloc] initWithImage:selectorImage];
customSelector.frame = CGRectZero; // Whatever rect to match the UIImagePicker
[self.view addSubview:customSelector];
[customSelector release];

Hacking the UI Element itself will take much more work, and this has to work as well.